MOSCOW -- Iran and world powers on Monday began to “engage” in detail about Iran’s nuclear program for the first time, although fundamental differences could prove unbridgeable at a second day of talks Tuesday, which could jeopardize the diplomatic track and eventually risk another Middle East war.

The P5+1 group (the U.S., Russia, China, Britain, France, and Germany) want Iran to give up its most sensitive uranium enrichment work, close a deeply buried facility and take steps that will forever keep it from acquiring a nuclear weapon.

Iran’s response Monday to that proposal – first put forward during acrimonious talks in Baghdad last month – focused on recognition of its right to enrich uranium for peaceful purposes and lifting crippling economic sanctions.

Neither point is part of the current P5+1 package, which will be gnawed over in final sessions in Moscow Tuesday.

“The difficulty here is not only quite a distance between the positions but also the sequencing ... what comes first, what comes next, what this reciprocity means,” Sergei Ryabkov, a Russian deputy foreign minister and negotiator, told journalists after the first day of talks. “It’s very complex. The logic of the negotiations is extremely complicated.”

In what could prove to be a critical encounter, Iran’s chief negotiator Saeed Jalili met after the formal talks with his Russian counterpart Nikolai Patrushev, head of Russia’s national security council and the former chief of Russia’s FSB, the successor to the KGB. It was far from clear if Russian influence with Iran would be enough to yield progress when talks resume. An Iranian diplomat close to the talks told The Christian Science Monitor that the morning session was “not good at all,” although the afternoon was “better.”

“Neither side is ready to say what their real points are,” the diplomat said, requesting anonymity due to the sensitivity of the talks. “They do not want to be in the position that the other side might guess their cards. Adding to that you could see huge lack of confidence….

P5+1 are not ready to give anything to Iran in response to Iran’s steps. (T)hey were here today just to have Iran’s response. It seemed that they did not have any clear vision (of) the next steps.”

Iran says it rejects nuclear weapons as un-Islamic; Israel says it could launch airstrikes to prevent Iran from having the capability to make an atomic bomb, and that negotiations with Iran are a waste of time.

So both the P5+1 and Iran have tried to spin the non-negative result of their “engagement” without deviating from their well-known positions.

“We had an intense and tough exchange of views,” said Michael Mann, spokesman for EU foreign policy chief Catherine Ashton, who represents the P5+1 at the talks.

“There was engagement,” said Mann. “We’ll have to wait and see tomorrow, I think, whether they come back with a positive attitude towards our proposals.”

The “clear” first step for the Iranians, he said, was to engage on their most sensitive 20 percent enriched uranium, which is only a few technical steps away from bomb grade.

Iranian officials have indicated since last fall that they were ready to deal on 20 percent enrichment. The Iranian diplomat said today that an integral part of Iran’s five-point counterproposal was that, in exchange for sanctions relief, Iran would “consider” a deal on 20 percent.